Meaning
A square floppy disk with a sliding metal shutter and a label area, the removable storage of early personal computers. Literally it is a disk for saving files.
Its lasting job is as the save symbol, so people drop it to mean save this or bookmark it for later: “This recipe is gold, 💾 saved.” It also carries retro computer nostalgia and often appears next to 🖥️ or 📼.